Rotary mowers and similar implements are commonly mounted in front of, under, or behind their towing vehicles. Typically the implements are pivotally connected to the vehicle to allow them to follow the contour of the ground and are powered by belt drive arrangements extending from a drive pulley carried on the vehicle to a driven pulley or pulleys mounted on the implement.
As these implements are moved over uneven ground, their pivotal connection with the towing vehicle permits them to rise and fall or "float" relative to their towing vehicle. When the implement "floats", its driven pulley and the V-belt trained around it will also rise or fall with respect to the drive pulley carried on the vehicle. Accordingly the belt will enter and exit the generally horizontal drive pulley at an angle above or below horizontal, thereby possibly causing it to be damaged as it twists into and out of the pulley grooves.
Such variation in the angle of entry into or out of the groove of the drive sheave will cause the V-belt to be tensioned unevenly across its band of cords. The cords provide strength to the belt and when overtensioned can become weakened or break. When the cords have been weakened, the life of the belt is reduced. If the cords break, the belt may immediately fail.
In an attempt to improve the alignment of belts used on "floating" implements with the drive sheave, pulleys and conical rollers have been provided above the belts, just ahead of their entry into and exit out of the drive pulley. While these pulleys and rollers have served to guide the belts into and out of the drive pulley groove, the belt is required to follow the periphery of the roller on pulley, which has a very small radius. Consequently, these pulleys and rollers tension the radially outermost cords of the belt to a greater degree and can cause them to weaken or fracture.